Brake structure



Dec. 9, 1930., J. SNEEQ BRAKE STRUCTURE Filed July 7, 1928 2 Sheets-Sheet l Dec; 9, 393m J.. @Een 1,784,395

STRUCTURE Filed July 7. 1928 E Smets-Sheet. 2

Patented Een. 9,y 1%3@ A T E JOHN SNEED, F FERNDALE, MICHIGAN, ASSIG'NOR T0 THE MDLAEXYD .STEEL PROD- 'CTS COMPANY, OF CLEVELAND, OHO, A. CORPORTON OF OEI@ enana sfrauoruna l Application illed. uly 7, ll. Serial No. l.

rlhis invention relates to vehicle brakes and particularly to the toggle mechanism for actuating the brakes.

l/Vhen a toggle is used as a 'spreading mechanism for a brake, it will be appreciated that the toggle and its actuating mechanism may well be arranged so that the toggle can not pass over dead center during application of the brake since the passing of the toggle beyond dead center releases the braking pressure. `Various devices have been employed to limit the travel of the toggle. For instance in my copending application Serial No. 30,- 459 filed May th, 1925, l have provided an abut-ment for engaging the yoke which was connected with the pivot pin of the toggle so that the pivot point could not be moved across dead center. However, ii a rigid linkage is employed between several brakes on dierent wheels, and fixed stops are associated with each toggle, there is the danger that one toggle may come upon its stop and tend to prevent urther application et' the other brakes. The pitch of the toggle in its working range might be made high so that the toggle would not be drawn near dead center under any conditions, but such an arrangement involves a loss of mechanical advantage, which ldesire to reta-in in my present invention. It is among the objects of my invention to arrange the toggle spreading mechanism between the ends of an internal expanding brake which can be normally operated at a high mechanical advantage close to its dead center position without danger of the toggle passing dead center and collapsing. Another object is to arrange at least one secondary point of Contact forat least one end ot the toggle which will comeinto operation as the toggle Lapproaches its primary position at dead center so that a secondary position of dead'c'enter will be established when the primary position is passed. Another object is to change the mechanical advantage ot the toggle from a high mechanical advantage as it approaches its primary point of dead center to a lesser mechanical advantage with a corresponding increased shoe travel from a glvenincrement of pedal depression.

.still further. objectis to arrange a pluspreading mechanism in the several brakes so that if through maladjustment or weer one of the toggles is drawn past its primary dead center, all of the toggles may be continued to be spread while the first one is approaching its secondary dead center 'at a reduced me chanical advantage. i Other objects will appear from the following description of my invention, reierence being had to the accompanying drawn ings illustrating a preferred form thereof. The essential characteristics are summarized in the claims.

ln the drawings, Fig. l is a partial elevation of the brake assembly; Fig. 2 is a section taken along the line 2 2 of Fig. l; Fig. 3 is a view similar to Fig. 2 with a toggle assuming position more nearly primary dead center; Figzl is a similar view illustrating the toggle in position beyond its primary dead center; Fig. 5 is a view similar to Fig. 2 showing a modiied form of my invention; Fig. 6 is a diagrammatic illustration ofthe angular relation of the parts illustrated in Figs. 2 and 3; Fig. 7 is a diagrammatic illustration of a toggle not embodying the feature of my invention and illustrating theangular relation of parts; Fig. 8 is a diagrammaticillustration of the hook-up or linkage employed to actuate' the brakes on the several wheels of a motor vehicle.

Referring particularly to Fig. 1, l choose to illustrate my invention in the environment of a well known brake which includes a full oating internal expanding brake shoe having an anchor between the ends of the shoes and having a toggle spreading mechanism between the same ends. There is shown the usual apron or backing plate A carrying an anchorpin l? which apr-0n closes the open 'Ill backing plate toexpand the toggle.

may comprise a served part 1 and a servo part 2. In the usual. forward motion of the vehicle the drum turns clockwise as indi-I cated by the arrow and in the usual application of the brake the servo part of the shoe 2 is expanded away from the anchor pin while the served part of the shoe 1 delivers the braking torque to the anchor'pin along anchor engaging surfaces F.-

To spread the ends of the shoe a toggle T is provided, which is universally connected at its ends to the ends of the shoes and has -a pivot pin 10 which is drawn toward 1the e.. ferring also to Fig. 2, the pivot pin l() may be engaged by a yoke Y which embraces a cable K. The cable K extends through an aperture in the apron and is drawn by tension exerted normal to the apron extending in the direction of the line V and may be` guided ina flexible conduit C. y

Referring particularly to Fig. 8, I illustrate diagrammatically a rigid linkage including conduits C, one of which is associated with each brake. The cables K pass through each of the conduits and are connected with pull rods R. The fore and aft pull rods are connected respectively to opposite ends of levers L which are secured to a'rotating cross shaft Q. The shaft Q may be rotated bysuch means as amanually controlled pedal U. Such' a linkage or hook-up is rigid as distinguished from mechanism having equalizing devicesbetween the several brakes. I wish to illustrate my invention vin connection with a,v rigid linkage wherein a given depression of the foot pedal causes like amounts of travel for each of the cables K and for at least the pivot points of all of the toggles in\the several brakes.

Referring back to Fig. 2, the ends of the shoes 1 and 2 pivotally carry pins 3 and vt` which extend Aparallel with thel anchor pin P. Each of the pins 3 and 4 carry vertically extending pins 5 'and 6 which are engaged by bifurcated ends of the toggle.' The toggle may comprise leversy 11 and 12 arranged so that the lever 11 engages the pin 5 and the lever 12 engages the pin 6.

Formed integrally with the lever 12 is an arm 13l which extends generally at right angles to the lever in a direction toward the apron and which engagesthe point 15 on the served end of the shoe as the toggle appreaches the position of dead center. Re-

ferring to Fig. 3 thearm 13 is illustratedin contact with the end of the shoe at 15 which maybe regarded as the point of secondary contact for oner end of the toggle. It will be noted in Fig. 3 that thepivot pin 10 kof the'toggle is approaching the primary dead center `line -N drawn through the pins 5 and 6, when contact isestablished at the that the effective mechanical advantage of thev toggle is sharply reduced.

If through `maladjustment or excessive wear of one of .the brakes its toggle passes primary dead center when all of t e brakes are being applied, that toggle will actin its secondary zone and that toggle will be acting at a relatively high angle or pitch while the other togglesv are approaching primaryl dead center and acting ata relatively low angle or pitch. Under such conditions if the cables K are all drawn equal amounts, the ends of the shoe in the most worn brake will be expanded the greatest amount, the result being that in the face of maladjustment or excessive wear in one or more of the brakes that substantially equal braking ei'ects will be had on all four wheels.

When the ends of the shoe repose on the anchor in idle position; the toggle assumes are spread when the drums rotate clockwise as viewed in Fig. 1, the pivot pin 10 follows an arc W'drawn about the point 5,as a center. It will be observed inFi 3 thatthe yoke Y is inclined from the line a maximum angle when the point 10 crosses the line N. It will be appreciated that it is desirable to keep this deviation as small as ossible durin the operation of the brake. ferring to 1g. 4 it will beob'seived as the toggle passes into its secondary zone that the point 10 continues to follow the-arc W and comes closer tothe line V. I have illustrated this diagrammatically in Fig. '6 wherein the greatest deviation of the vpoint 10 from the line V is indicated at 30' and a lesser deviationindicated at 31.

Referringto Fi grammatically` a simple toggle not embody ing the principle of my invention in which the levers 11a and 12a are necessarily lon r than'the levers 11 and v12 to spread the ins 3a and '4a a distance equal to the sprea this ligure that t e pivot pin 10a follows the are W and ydeviates a greater amount from the' line V than 'it' does 'as illustrated in either Fi 4 o r 6.

Referring back to Fig. 4, I show the ivot point 10 approaching the secondary dea center and priorto its extreme position I provide that the yoke Y will contact at its inner end 'its g. 7, I have indicated dia- Aillustrated in Fi 4; It will be observed in with the end of the conduites at 40. As memtioned above, this relation is shown 'in my copending application and Ioxily contemplate this condition 'to exist under the most extraordinary circumstances and provide this arrangement in my present invention in contemplation of emergencies. i

Referring particularly to Fig. 5 l show a modified form of my invention wherein the toggle has a lever 12 with an arm 13 and wherein the lever 11 has a similar arm 13a. rlhe operation of such a toggle would be in all respects similar to the toggles described above except that the angular and bodily movement of the yoke Y would not be reduced during the application of the brakesy in the usual forward movement of the vehicle as it is in the preferred form of my inven, tion, as illustrated for instance in Fig. si.

From the foregoing it will appear that l have provided a spreading mechanism for a brake which has a high safety factor and insuresthe uniform action of a lurality of brakes and distributes braking oad among several brakes including those excessively worn or poorly adjusted. While l have illustrated and described a preferred form of my invention and shown it in connection with a particular type of brake and associated with a rigid linkage, l do not care to be limited in the scope of my patent thereby or in any manner, other than by the claims appended hereto.

l claim l. Togglespreading mechanism compris ing a pair of levers pivoted together, one of said levers having a normally idle arm adapted to include the fulcrum point for one end oi the toggle when the pivot point ont' the toggle approaches the line which joins the normally operative ends of the toggle.

2. The combination. of a toggle comprising a pair or levers pivoted together, pins normally engaged by the ends of the toggle, a member associated with one of said pins, an arm associated with one oi said levers and adapted to engage said member as the toggle approaches the position ot dead center.

3. A toggle comprising a pair of levers pivoted together, one of said levers havin an arm, in combination with means engaged by one end of the toggle, said means having a part engageable by said arm las the toggle approaches primary dead center and means for pulling the pivot point of said toggle and moving said 'lirst named means until said arm engages said part,'whereby a secondary n, line of dead 'center is established toward which thepivot point may be drawn without collapsing the toggle.

" d. Toggle spreading mechanism lfc'omprising a pair of levers of which v'at least one of the levers has an arm extending in the plane of action of the toggle and in the direction of motion of the levers when the toggle is attened in combination with a member en gaged by said lever having a part positioned in the path of movementof saldjarm adapted to engage said arm at a point opposite from the pivot point of the toggle whereby said lever normally fulcrums upon said member and has a secondary fulcrum point where the arm engages said part.

5. Toggle spreading mechanism for the ends of a brake shoe including .apair of levers having their inner ends pivoted together at the pivot point of the toggle and having their outer ends engaging `opposite ends of the brake shoe, said outer ends having a plurality of points engageable with the said shoe ends, whereby a line drawn through a pair of such points determines the primary dead center of the toggle and a line drawn through a diiiierent pair of such points determining the secondary dead center for said toggle. f

6. Toggle spreading mechanism including a pair of arms having their inner ends pivoted together and constituting the pivot pointor the toggle and having primary ulcrum bearing points at their outer ends, said arms having additional and secondary bearing points at their outer ends which determine a secondary position of dead center for the toggle along a line parallel to the line of primary dead center.

7. ln a brake, a friction device having a I part movable into engagement with the brake drum, toggle mechanism for moving said part including a lever pivotally connected with said part, said lever having an arm spaced from said part when the brake is idle and movable into engagement with said part at leastwhen the toggle is flattened.

8. ln a brake, a friction device having a part movable into engagement with the brake drum, toggle mechanism including a lever pivotally and slidably connected. with said part at one point, said lever having an arm spaced from said part when the brake is idle andmovable into engagement with said part at a point spaced from the First point at least when the toggle is iiattened and establishing i a diderent pitch for the toggle at the moment oi engagement.

9. ln a brake, the combination of a friction device, a toggle for actuating said friction device having a lever connected with at least one end of the friction device, a fulcrum pin carried by the end oi the friction device and engageable with the end oi? said lever, said lever havin an arm normally spaced from the end of t e said friction device and movable into enga ement therewith as the toggle is flattened, said arm contacting with the end of said friction device and establishing a secondary point of contact for the togglewhereby-the end of the friction device may be moved by pressure exerted through said arm after the end of said lever ceases to engage said pin.

l0. ln a brake the combination 'of a shoe having an anchored end anda tree end, thrust having an anchored endand a free end, an

apron having an opening adjacent the ends of the shoe,a toggle for spreading the ends' of the shoe apart and disposed in the plane normal to said apron, said toggle normally having one point of contact with each end of the shoe which points determine the line of primary dead center for the toggle, said toggle having a projecting part near the free end of the shoe extendin toward the a ron and adapted to enga e t e free end o the l shoe at least when t e pivotpoint of the toggle approaches the line of primary dead center, said part contacting wit the free end of the shoes at a point which establishes a line of secondary dead center and means extending through the opening in said apron and connected with the `pivot point of said toggle for drawing ther ivot point throu h its line of primar dea center toward t e line of secondary ead center.

12. In a brakev he combination of av shoe having an anchored end and a free end, an apron having an o 'ening adjacent the 'ends of the shoe, a togg e for spreading the ends of the shoe a art and disposed in a plane normal to sai apron, said toggle normally having one point of contact with each end of the shoe which points determine the line of primary dead center for the toggle, said toggle having a projecting part near the free end of the shoe extendingv toward the apron and adapted to engage the free end o the shoe -at least when the pivot point of .l the toggle approaches the line of primary dead center, said part contacting with the free end of the shoes at a point which establishes aline of secondary dead center and no ondary zone `of* operation entered into when means extending through the opening in said apron and connected with the pivot point of said toggle for drawing the cpivotv point through its line of primary dea 'center toward the line of secondary dead center, and means for limitin the travel of the toggle short of the line o secondary dead center.

13. In a brake the combination of a friction device, toggle mechanism for actuating said friction device, said toggle mechanism having a primary zone of operation of increasing mechanical advantage and a secthe toggle approaches the position of highest mechanical advantage in its primary zone, the initial mechanical advantage in the secondary zone being substantially less .than the the shoe having an armfinal mechanical advantage in the primary Y at least one end of the shoe madewhen the toggle approaches a line joining the first named points of contact whereby in a given position the toggle has two points of contact' at one end of the shoe which are spaced apart, the auxiliary point of contact changing the effectivel pitch of the toggle when the spreading force is delivered through that oint.

15. In a brake the combination o an apron,

a friction device having separable ends, and toggle mechanism for spreadin said ends, .said toggle comprising a pair o levers having their inner ends pivotally connected and having their outer ends normally engagin opposite ends of said friction device, eac of said levers having arms projecting toward the apron and in the direction of active motion of the toggle, said arms being engageable with opposite ends of said friction device at least when the toggle is flattened, whereby additional points of contact are established for the ends of the toggle to permit further movement thereof.

v16. Toggle spreading mechanism for a brake' comprising a pairof levers pivoted together, at least one of said levers having a normally idle portion positioned to include the fulcrum point of one part of the toggle when the toggle approaches dead center and thereb establish a new zone of operation beyon the original dead center.

'los

17. Toggle spreading mechanism including a pair of arms having their inner ends pivoted together and constitutin the ivot oint for the toggle and having fu crum aring points at their outer ends, said arms having additional secondary bearing oints which determine a secondary position o dead f center for the toggle.

18. A toggle spreading mechanism according to claim 17 wherein atleast one of said arms has a slidin las well as pivotal connection at one of sai points.

19. In a brake having a friction device with se arable ends the combination of a toggle aving arms connected together at their near ends forming the pivot oint of the toggle and connected at their ar ends to the ends of the friction device, means whereby the pivot point i's drawn in to line with the ends ofsaid arms-to a position of primaryV dead'center, and means for estab'- lishin a secondary position of dead center where y said pivotpoint maybe drawn bef signature.

'Jomr sNEEn 

